1. Field of the Invention
The present invention relates to a novel carbon nano-particle and a method of preparing the same and a transparent conductive polymer composite containing the same. More particularly, the present invention provide a novel carbon nano-particle in which carbon atoms forming a particle are bound in the graphite structure, and the mean diameter of the particle is 1 through 50 nm, preferably, 1 through 10 nm, and which has the shape of sphere, rod, or other shapes, and a novel method of preparing the carbon nano-particle, and a polymer composite, containing the carbon nano-particle, with the transparency as well as the excellent conductivity, in any case, the ferromagnetism.
2. Description of the Background Art
In recent years, information technology (IT), biotechnology (BT) and nanotechnology (NT) draw an intensive attraction as highly advanced technologies. Of them, the intensive researches in the nanotechnology (NT) are being conducted as to fullerenes, carbon nanotubes, etc., being formed of only carbon atoms and having the size of angstrom (Å) or nano meter (nm).
The fullerene is generally formed in a football shape in which 60 carbon atoms are bound to form twenty hexagonal structures and twelve pentagonal structures. The number of carbon atoms forming the fullerene is 60, 62, 64, 66, etc., depending upon the kinds thereof. The smallest C60 fullerene has a diameter of about 7 Å and the shape of sphere. The C70 fullerene has the major axis of about 8 Å and the minor axis of about 7 Å and is formed in a rugby ball shape.
The carbon nanotube is formed in the structure in which a graphene sheet is roiled in a cylindrical shape and has the diameter of 3.5 through 70 nm and the length (μm unit) of a few hundreds through a few thousands times of the diameter. The carbon nanotube can be classified into a single walled tube formed of one graphene sheet and a multi-walled tube in which 2 through 30 graphene sheets are formed in a concentric circle. Shapes of the carbon nanotube and methods of preparing the same are disclosed in U.S. Pat. No. 4,663,230.
The fullerene and carbon nanotube are prepared by a basically same method or similar method. Namely, they are made when carbon atoms vaporized are condensed under an inert environment. In order to increase the productivity of them, various methods have been developed. As examples of methods of preparing the carbon nanotube, there are an arc-discharge method which evaporates carbon atoms based on an electric discharge of two graphite rod electrodes; a laser vaporization method which evaporates carbon atoms radiating a laser to graphite; a plasma enhanced chemical vapor deposition method which glow-discharges carbon atoms using the high frequency electric field; a thermal chemical vapor deposition method; and a vapor phase growth method.
The above carbon nano-materials are expected to be applied to many fields in the future. While uses of the fullerene with the small size of less than 1 nm have been not developed yet, uses of the carbon nanotube are realized to various purposes such as reinforcing agents of composite material, anti-static electricity materials, and electromagnet-shielding materials, and the like.
For example, according to the U.S. Pat. No. 5,098,771, it is possible to obtain a high conductivity in such a manner that 0.5 through 10% by weight of carbon nanotube is added to a thermoplastic resin such as polyethylene, polypropylene, polyamide, polyvinylchrolide, etc. or a thermosetting plastic resin such as saturated polyester, alkyd, epoxy, etc. However, where carbon nanotubes are added to a transparent resin in order to prepare an optically-transparent, conductive film, a strong aggregate power is generated between carbon nanotubes during the coating process to black the film, so that the transparency of the resin is significantly decreased. For preparation of a transparent composite, the size of particles added to a resin or the size of particle aggregators should be below the half of the shortest wavelength of a visible ray (below about 200 nm).
U.S. Pat. No. 5,853,877 discloses a method for preventing aggregation by the surface-treating process of a carbon nanotube and thereby increasing the transparency of a composite. However, since the above method needs the use of a strong acid such as sulfuric acid, it makes the process difficult and also the composite containing such surface-treated carbon nanotubes has the transparency worse than Indium Tin Oxide (ITO).
Therefore, the so far known carbon nanotubes are not capable of effectively forming a transparent composite because of the limit of their size or the limit of methods of treating them.
Furthermore, since the so far developed methods include a step for evaporating carbon atoms, the carbon nanotubes prepared therefrom are relatively expensive; therefore, it is impossible to implement a mass production on the basis of these methods.
Therefore, the need for a novel carbon nano-material is increasing which has the high conductivity like carbon nanotubes and the size of less than ½ of the shortest wavelength of a visible ray and can be also prepared at a lower cost.